1. Field of the Invention
The present invention relates to a technology effective in being applied to a device and a method of coding and decoding an image captured at multi-points of view.
2. Description of the Related Art
Over the recent years, a technology of utilizing a dynamic image (moving picture) captured simultaneously at multi-points of view has been focused. What has been impossible to a conventional stereo-camera system is made possible by utilizing this type of dynamic image. For example, a user is enabled to watch a camera dynamic image at the multi-points of view without using a stereoscopic display. To be specific, a scene of a concert is imaged simultaneously at the multi-points of view, whereby the user is enabled to watch a situation of the concert not from a single viewpoint but from arbitrary viewpoints such as in a crosswise direction and a rear direction.
By the way, generally, a data size of the dynamic image (moving picture) is extremely large. Therefore, it is disadvantageous in terms of a transmission speed and a cost to accumulate media data and transmit the data via a network without compressing the dynamic image data. Hence, such technologies have been developed that the dynamic image is compression-coded by a reversible or irreversible method. These technologies are exemplified such as MPEG-1, MPEG-2 and MPEG-4 standardized by Moving Picture Experts Group (MPEG).
The number of dynamic images, however, increases with a rise in the number of multi-points of view at which to capture the images simultaneously (a rise in the number of cameras). Therefore, a total data size of the dynamic images captured simultaneously at the multi-points of view rises as compared with the data size of the dynamic images captured by use of the single camera. Hence, a demanded technology is a technology of efficiently compression-coding the data of dynamic images captured simultaneously at multi-points of view.
A technology of improving prediction efficiency by use of correlativity between the dynamic images captured at the multi-points of view is proposed to cope with such a problem. In this type of technology, the coding efficiency is improved as the prediction efficiency is improved. The correlativity between the dynamic images captured at the respective viewpoints implies that an object and a background projected on a camera at a certain viewpoint are also partly projected on a camera at another viewpoint. For example, when a frame on the camera at a certain viewpoint is compared with a frame captured at the same time on the camera at another viewpoint and if the two cameras capture the image in near positions and in near directions, there might be a case where the same object and the same background are imaged. Therefore, the frames captured at the same time by the different cameras are deemed as the frames captured by the same camera, whereby the predictive coding employing the motion vector can be performed. For instance, the coding efficiency can be made higher in the case of motion-prediction-coding the frame of the latter camera by employing further the frame of another camera (the former camera) than in the case of motion-prediction-coding the frame by use of only the frame captured by the same camera (the latter camera) as done so far. In this case, the motion vector is equivalent to a parallax between the two cameras. This type of technology is exemplified by Patent documents 1-7.    Patent document 1: Japanese Patent Application Laid-Open Publication No.2001-186516    Patent document 2: Japanese Unexamined Patent Publication No.2002-523943    Patent document 3: Japanese Patent Application Laid-Open Publication No.2002-300607    Patent document 4: Japanese Patent Publication No.3426668    Patent document 5: Japanese Patent Application Laid-Open Publication No.06-98312    Patent document 6: Japanese Patent Application Laid-Open Publication No.10-191394    Patent document 7: Japanese Patent Application Laid-Open Publication No.2000-23918